Lubricating oil



?atented Oct. 25, 1938 maximum; 011.

Troy lee Cantrell and James Otho Turner, Lansdowne, Pa, assignors toGulf Oil Corporation, Pittsburgh, Pa, a corporation of Pennsylvania NoDrawing. Application August 31, 1936,

Serial No. 98,827

and its performance improved by the presence therein of a small amountof an alkyl thioether of ortho-amino-benzene; and it also comprisesmethod of making an improved oil wherein such ortho-aminophenyl alkylthioether is incorporated, in the oil prior to application of thelubricant to a hearing; all as more fully hereinafter set forth and asclaimed.

Recent developments in the design of mechanical equipment for generatingand transmittin power, and particularly in the automotive field, havenecessitated new bearing metals with special properties in thisrelation. Among these new bearing materials are binary and ternaryalloys of the metals mentioned above. Cadmiumsilver-copper,cadmium-nickel-copper, copperlea'd-nickel, etc., alloys are in use. Oneternary alloy current used in automobile engines is an alloy of cadmiumwith minor amounts of both silver and copper. Under the conditionsimposedby modern engineering design, these new alloy bearings arecommonly subjected to more severe operating conditions than were usualin the older art: to higher bearing loads, higher rubbing speeds andhigher temperaturesof operation. It is found that in actual use underthese conditions there often develops quite serious destructive actionon the bearing surface by mineral lubricating oils, even by thosestandard commercial oils give ing particularly good results with theolder hearing metals under the earlier operating conditions. 45 Thedestructionof the bearing metal probably results from action ofdeterioration products developed in the oil. An'object'achieved in thepresent invention is the production of lubricating oils improyed forthesenewer conditions of use and b which are characterized by reductionor elimination of destructive action on the newer bearing metals bydeterioration products in the oil.

We have discovered that the alkyl thioethers of ortho-amino benzene,incorporated with lubricants, are capable of achieving the objects ofthe 5 present invention, the alkyl thioethers such as those containingthe various amyl groups being particularly eflective. Byadding smallamounts of such a thioether to the mineral oil or lubricant, we obtainimproved lubricating composi- 10 tions which satisfactorily lubricatealloy bearings. Incorporated in mineral oil, these thio'ethersretarddestruction of the bearing metal. Also, the film strength of thelubricant is increased, the thioethers imparting extreme pressurecharacteristics to the oil. The character and amount of addedimprovement agents, here employed, are such that the normal physicalproperties of the oil, such as viscosity, gravity, color, etc., are notsubstantially altered. 'Certain properties of the lubricant are improvedwithout sacrificing the other desirable properties.

We obtain improved mineral oils and lubricants suitable for lubricatingsuch bearings under a wide. range of service conditions. The newcompounded lubricant satisfactorily lubricates the new alloy bearingseven under high unit pres sure, high bearing speedsandhigh operatingtemperatures. When prepared from suitable mo-' tor oils, the presentimproved compositions are excellent lubricants tor the modern automobileengine. They satisfactorily lubricate the bearings without anydestruction of the special hearing alloys now used, even in the presenceof a free circulation of air.

' Ordinarily between 0.05 and 0.50 per cent, by weight on the oil, ofthese thioethers is sufdcient to produce a satisfactory lubricant.However, in some cases larger amounts of the thioethers may be employed,for instance, with those oils of more pronounced destructive tendency.As much as 2 per cent of thioether may sometimes be added withadvantage. The particular proportions depend upon the particularthioether and lubricating base employed and the particular type oflubricant desired.

When larger amounts are employed, extreme pressure characteristics arealso imparted to the mineral oil or lubricant. In many cases, the loadcarrying capacity of the lubricant may be in- QS-R NHr

wherein R represents an alkyl group. As a class, these thioethers aresoluble and miscible with mineral oils in substantial proportions. Wehave found that they are sufiiciently soluble and miscible to permitincorporation with the mineral oil of an amount of thioether suflicientto obtain the described improvement.

These thioethers may be obtained from thioethers of ortho-nitrobenzeneby reducing the nitro group to an amino group employing suitablereducing agents such as hydrochloric acid and tin, and then recoveringthe thioether of ortho-amino benzene so produced; the following equationillustrating the typical reaction:

NO: NHa wherein R represents an alkyl group.

In our copending application, Serial No. 98,828,

filed August 31, 1936, we have described and claimed methods ofpreparing the said thioethers of ortho-nitrobenzene and converting theminto the corresponding amino compounds and the various new thioethers soobtained.

In the present invention the reaction products so obtained may beemployed or, if desired, they may be further purified by the variousmethods set forth in said application Serial No. 98,828, beforeincorporating them in the lubricating base.

As stated ante, thioethers containing alkyl roups, such as the variousamyl groups, are particularly effective for the present purposes. Allthe amyl groups give good materials for the present purposes. Of these,the normal-amyl thioether of ortho-nitrobenzene is typical; the amylcompound has the following formula:

in certain relations. Other alkyl thioethers which are advantageous forthe present purposes are Ortho-aminophenyl-ethyl-thioether,

Ortho-'aminophenyl-butyl-thioether,

Ortho-aminophenyl-propyl-thioether.

These specific thioethers, as a sub-class, may be represented by thefollowing formula wherein n is to 3. However, in the broad practice ofthis invention other thioethers of orthoaminobenzene may be employed.

These thioethers are quite stable, even ,at the elevated operatingtemperatures usually encountered in the lubrication of alloy bearings.Also, they are substantially neutral in reaction. Most of them areliquids at normal temperatures although some are solids melting atrelatively low temperatures. Generally, their color varies from a paleyellow to a reddish yellow and when dissolved in the mineral oil, thecolor of the oil is only slightlyaltered. The amyl and ethyl thioethersare liquid; .they being typical, some of their properties here importantare given in the following table.

The amyl thioether is made from a commercial amyl mercaptan and containsvarious amyl groups. Table A Amylthlo- Ethylthioether ether Gravity: B14. 8 24. 6 Viscosity, SUV' 100 F 42.8 39. 5 Pour, F O 0 Color, N PA. 65. 6 Sulfur: Percent l6. 4 20. 8

From the above table the variation in physical properties with thelength and complexity of the aliphatic constituent of the thioether isgenerally indicated. By employing thioethers containing other alkylgroups, these properties may be varied at will to obtain certainadvantages in particular embodiments of the present invention. This maybe readily done by selecting the desired mercaptan in making thethioether by the reactions described ante.

Generally, the thioethers here employed are readily miscible andcompatible with petroleum oils in the percentages necessary for thepresent purposes. They may be incorporated with the mineral oil orlubricating base in any suitable manner. They may be dissolved in theoil by, simply mixing the thioether with the oil and slightly warmingwith agitation to obtain uniform lubricants. -Warming to temperaturesbetween 100 F. and 180 F. is usually sufficient; the thioethers beingreadily soluble. With the heavier and more viscous lubricating oils thiswarming is advantageous since the heating lowers the viscosity of theoil facilitating the blending. In some cases, the thioethers may bedissolved in suitable volatile solvents and the solution added to theoil, the solvent being subsequently distilled off. This solvent methodis particularly eifective with the solid thioethers. Also, thethioethers may be first dissolved in a suitable lubricating oil to forma master batch which is subsequently blended with more lubricating oilto give a range of lubricating compositions as desired. Likewise thecompounded lubricant may be converted into thickened compositions orgreases in any of the usual ways. Sometimes the thioether may bedirectly added to metal soap greases or other compounded lubricants inwhich a petroleum oil is the lubricating base.

In the practice of the present invention any suitable lubricating oilbase may be employed, either heavy or light oil. Ordinarily it is bestto select a good grade of lubricating oil which has suitable initialproperties for. the particular lubrication'requirement. Then theaddition of the thioether produces the additional desiredcharacteristics of restraining their destructiveness toward the neweralloy bearing metals, etc. That is, petroleum oils and lubricants of theusual grades may be employed in practicing this invention. The oilsfalling within the well known S. A. E. classification are among thosewhich can be advantageously improved by our invention. Likewise, speciallubricants such as obtained by blending certain non-petroleum oils withmineral oil may be improved by the addition of these thioethers.

The deterioration of bearings by particular oils under drastic serviceconditions may be readily observed by visual inspection, but a speciallaboratory test is necessary to readily and quickly determine it on astandard, comparable and reproducible basis and to really evaluatecommercial lubricants for such alloy bearings. We have devised asatisfactory accelerated test procedure which is as follows.

An alloy bearing shell of certain commonly used standard dimensions issubmerged in 300 cc. of the oil or oil composition in a 400 cc. pyrexbeaker and heated in a thermostatically controlled oil bath to 175C.(374 F.) and air, at the rate of 2000 cc. per hour, is bubbled throughthe oil in contact with the bearing shell. At the end of 48 and 96hours, the loss of weight and the condition of the bearing shell aredetermined. This test will hereinafter be referred to as our standardlaboratory test.

In determining the loss in weight the bearing shell is washed free ofoil and dried before weigh- When determining the efiectiveness ofvarious improvement agents the usual procedure is to run a bla testsimultaneously with the oil composition being tested, employing for thatpurpose a sample of the untreated oil.

In such tests it is advantageous to employ commercial bearing shells.These shells comprise a suitable metal backing faced with the alloybearing metal. In the above test, the air is bubbled against the alloybearing face. In this way, the actual bearing face is subjected tosevere deteriorative conditions. By comparison of the results of suchtests with actual service tests, we have found them to be in substantialagreement as to the suitability of particular lubricants.

In testing our lubricants, we have employed, among others, bearings ofthe following approximate composition:-

1. Cadmium-silver alloy. (3-8 7610.

Per cent Cadmium 98 Silver 1 Copper 1 2. Lead-copper alloy. 9020 CA.

Per cent Lead Copper 7 53 Nickel 2 loy facing of only 0.008 in. to 0.012in. thickness on a highly resistant backing and the observed losses inthe reported tests often represent a loss of the order of 10 per cent ofthe alloy facing.

The specific examples and tests givenpost are illustrative of the detailembodiments of the present invention.

Example 1.Into a suitable vessel there were introduced 1000 gallons(approximately 7200 lbs.) of Pennsylvania motor oil S. A. E. 10 gradeand the oil was warmed to 160 F. Then 15.3 pounds of the amyl thioetherof orthoaminobenzene (0.20 per cent by weight on the oil) was graduallyadded and the mixture agitated until a uniform blend was obtained; aboutone hour being required. In agitating the mixture ordinary mechanicalagitators may be employed or a current of air may be passed through thewarm mixture, to produce uniform blending. The amyl thioether used inthis example had the properties given in'Table A ante and was a mixtureof isomeric amyl compounds, it being prepared from a commercialmercaptan.

The properties of the original and improved motor oil are as follows:

From the above table, it is clear that the addition of the amylthioether of ortho-aminobenzene does not substantially change thecommonly determined physical properties of .the oil. When tested by thestandard laboratory test given ante, using a commercial bearing shellfaced with a cadmium-silver alloy (C-S 7610), the following results wereobtained in a 48-hour test run on the original oil and on the improvedlubricant:

Table 0 fi gg fl Original oil Improvedlubricant Gram Grams 27. 5603 27.3155 27.0818 27. 3145 -00.4785 00. 0010 Substantial loss Insignificantloss Bearing ap anee Badly etched and pitted No change (after test Fromthe above results, the beneficial effect of the thioether as animprovement agent for the oil is quite apparent. This improved lubricantwhen tested in an automobile engine equipped with like bearings washighly satisfactory and no destructive effect on the bearing wasobserved after a severe test run. Thus the standard laboratory test andactual service test gave similar results.

The improved motor oil obtained in Example 1 also has increased filmstrength and load carrying capacity, that is, the incorporation. of thesaid amyl thioether imparted extreme pressure characteristics to thelubricant. This is one of the advantages of employing these thioetherser ortho-aminobenzene.

" Example 2.Emplo,ying the same blending procedure as for Example 1 andsubstituting a highly refined motor oil of S. A. E. 30 grade made fromPennsylvaniacrude and incorporating 1 per cent ing of 16 pounds undersimilar conditions. These weight loadings on the Almen lubricatingtesting machine produced bearing loads respectively of 4000 pounds persquare inch and 8000 pounds per square inch. Clearly, very smallproportions of these thioethers of ortho-aminophenyl alkyl thioethersare capable of improving the film strength and load carrying capacity ofhighly refined lubricating oils by 50 to 100 per cent.

Example 3.--Employing the procedure of Example 1 and substituting ahighly refined Pennsylvania motor oil S. A. E. 20 grade in lieu of thelubricating base employed in Example 1, still another improved lubricantis obtained.

In the above examples, other thioethers may be used in lieu of the amylderivative and similar improvements obtained.

The above examples are but illustrative embodiments of the presentinvention and in practice other embodiments may be used. That is, thepercentage of thioethers employed may be varied as indicated, accordingto the particular properties desired in the final lubricant. Likewise,the lubricating base itself may be selected according to the type offinal lubricant to be produced. For instance, any of the usual greasesor the usual blends of mineral and non-mineral oils may be employed as alubricating base in making lubricants of our improved type. The additionof the thioethers to these lubricating bases produces a. likeimprovement in film strength and reduces their destructiveness towardthe newer bearing alloys. When incorporating the thioethers in a greasecomposition or like thickened lubricant, mechanical agitators ratherthan a current of air are employed to obtain uniform mixing andblending, That is, the thioether and grease may be compounded in theusual mixers such as blade mixers, equipped with heating jackets.However, in making such greases the thioethers may advantageously firstbe incorporated with the oil base according to the procedure of Example1 and then the metal soap or the thickening agents added to the improvedoil, in the ordinary way to produce the desired grease compositions. Inother words, the improved mineral oils of the present invention may beused in lieu of the ordinary oils in making special lubricatingcompositions such as greases, etc.

The ethyl thioethers of orthonitrobenzene and other thioethers may beemployed in lieu of the amyl thioether in the examples given ante. amyland like alkyl thioethers being particularly effective are ordinarilyemployed. With proper blending, good lubricants may be produced with allthese thioethers compounded with various petroleum oils or mineral oillubricants.

As stated ante, the incorporation of these thioethers with thelubricating base produces several improvements in the final lubricantwithout deleteriously aiiecting the desirable properties. While theexact reasons for the improvements obtained are not fully known, we aresatisfied with observing and utilizing the actual improvements ob- The:

materials wherein the substituent group is a ni-- tro group. Certainspecial advantages are secured with each of these types of materials.

Having described the methods of making and using such improvedlubricants, what we claim is:

1. A method of lubricating bearing surfaces in internal combustionengines when subjected to conditions of operation which comprisesmaintaining between bearing surfaces, one of which is an alloy formedchiefly of a metal-of the class consisting of cadmium and copper, a filmof a lubricating oil which initially produces an effective lubricatingaction but which would normally tend to corrode theaforesaid alloy,andmaintaining the eifectiveness of the lubricating oil by means ofbetween .02 per cent and 0.20

per cent, by weight on the oil, of an ortho-aminophenyl alkyl thioetherdissolved in such lubricating oil, said alkyl thioether having thefollowing formula:

3. As a new and improved lubricant capable of lubricating cadmium-silverand other special alloy bearings at high temperatures, pressures andspeeds, without corroding such alloy bearings, an improved motor oilcomprising a mineral oil containing a minor amount of .an alkylthioether of ortho-amino benzene dissolved therein, said mineral oilbeing'a motor oil which while capable of initially producing aneffective lubricating action, would normally tend to corrode saidalloys, under said conditions, and the amount of said thioether beingsufiicient to 'efiectively and substantially retard the destructiveaction on said alloy bearings which would normally occur in the absenceof said thioether, said alkyl thioether having the following formula:

4. As an article of manufacture, a. new and improved lubricantcomprising a major propor- NH: wherein It represents an alkyl group, andthe 10 amount of said thioether' being suillcient to substantiallyimprove the lubricating qualities of said lubricating oil.

5. The new and improved lubricant oil claimvi wherein said minerallubricating oil contains from 0.02 to 2 per cent oi said alkyl thioetherof ortho-aminobenzene dissolved therein.

6. The new and improved lubricant of claim 4 wherein said thi'oether isortho-aminophenyl amyl thioether.

7. The new and improved lubricant of claim 4 wherein said thioether is.ortho-aminophenyl ethyl thioether. i

TROY LEE CANTRELL. JAIMES O'I'HO TURNER.

